This invention relates to devices for imprinting nameplates and similar workpieces. More particularly, this invention relates to electrically actuated markers which utilize a keyboard for indexing a rotary marking dial which imprints various information on metal or plastic nameplates and the like.
Marking machines of this general type provide an indexing table to hold and position a nameplate or similar workpiece to be imprinted and to space the characters imprinted thereon during marking. Imprinting is effected using a stamping means such as an interchangeable marking dial provided with the desired characters. The marking dial is indexed and actuated using a typewriter-like keyboard and electromechanical devices associated therewith, so that when a key is depressed the marking dial is first indexed with a desired character in marking position and then displaced a predetermined distance to execute a marking stroke. Thereafter the indexing table is advanced a predetermined distance to position the workpiece for the next marking stroke.
For quality imprinting at relatively high speed it is important that positive and reproducible indexing of the marking dial is obtained when the marking machine is in operation. Furthermore, it is desirable to accommodate a maximum number of characters on the marking dial without unduly increasing the size thereof. Yet the more characters are provided on a given marking dial, and the closer the spacing therebetween, the more critical becomes the indexing problem.
Heretofore known marking machines utilize a ratchet gear means mounted on an indexing shaft which also carries the marking dial in combination with a plurality of spaced detents adapted to engage and hold the ratchet gear in a predetermined position. For even spacing of imprinted characters the detents have to be carefully aligned with the ratchet gear and with each other; however, when the marking machine is used the detents tend to become misaligned due to the repeated impact of the ratchet wheel and as a result produce uneven spacing between characters.
Accordingly, it is an object of the present invention to provide an improved marking dial indexing assembly which obviates the aforementioned shortcomings and which utilizes a single detent means yet which does not require an increase in the diameter of the lettering dial for the same number of marking characters. Still other objects of this invention will become apparent upon reference to the ensuing specification, the accompanying drawings and the claims.